We have examined several peptides derived from pituitary proopiomelanocortin for their effects on cortisol and aldosterone secretion in the autoperfused dog adrenal glands. Synthetic human Beta-lipotropin [Beta-LPH-(1-91)], which is released from the pituitary gland concomitantly with ACTH, produced a significant increase in aldosterone, but not cortisol secretion. The time-course of the increase in aldosterone was similar to that previously described for Beta-endorphin [Beta-EP or Beta-LPH (61-91)], but the dose of B-LPH needed to produce an equipotent response was larger. Synthetic Gamma-lipotropin or synthetic Beta-melanotropin (Beta-MSH), the C-terminal portion of Gamma-lipotropin [Gamma-LPH or Beta-LPH-(1-58)], had no effect on either cortisol or aldosterone secretion. Furthermore, Alpha-EP (Alpha-endorphin, Beta-LPH (61-76)] or Gamma-EP [Gamma-endorphin, Beta-LPH (61-77)] did not affect the secretion of either adrenal steroid. Taken together, these data indicate that 1) Beta-endorphin is the only Beta-LPH-derived peptide that selectively stimulates aldosterone production in vivo; and 2) the aldosterone-secreting activity is contained in the C-terminal sequence of Beta-EP.